1:96 USS Dolphin

[RCENGR]

This thread is to document the build of a 1:96 scale USS Dolphin that is being built in collaboration with SVilling. I'm the chief engineer and master mechanic, while Steve is owner, financier, program manager and sub expert. We started this project once we decided that we would attend the RC Subfest Redux at the end of April. Steve's requirements were for a 1:96 model (I did try and talk him into 1:72), RCABS, and an AD2.He wanted a z cut hull with the cut line at the waterline instead of in the middle. He gave me a 1.75" OD x 1.625" ID x 12" tube to use as the WTC.

I fired up the CAD program and had a hull done in a couple of evenings, due to the simple nature of the design. The first design decision was how to access the linkages in the tail. I played with a hatch, but ultimately ended up with a tailcone that bolted on with 4 2-56 bolts.

Next was figuring out how to do the linkages. I decided early on that the pitch planes would be done externally. That left the rudder yoke to go inside the hull, which was 0.75" diameter at that point. I started by soldering 1/16" wheel collars to some 1/4" square tubing. That worked, but it was a little wonky, so I drew up a 3D printed part that used 1/16" wheel collars.



I included supports for the WTC in the hull.


The Dolphin in its carrying case

[redboat219]

No photos.

[He Who Shall Not Be Named]

You can easily encase all the linkages within that stern:

[RCENGR]

Designing the WTC was where all the work was. I initially split the cylinder into three sections, 4" for the Rx, battery, and ballast pump/solenoid, 4" for the ballast tank, and 4" for the motor and servo section.

I started with the servos. I adapted the concept of the 3DP linear servo setup as provided in the Nautilus Drydocks 3DP file section. The design uses HS-55 servos and 1/16" x 1/8" Teflon tube instead of brass for the linear bearings. The servo arms would have interfered if I put the servos side by side, so I rotated one of them 180 degrees to get the needed clearance. The motor is a 280 size brushed motor with flat sides that I use a lot on my surface ships. It has a Kv of about 1000 rpm/volt so it works well at 6-8 volts on props less than 1.25". The ESC is taped to the top of the motor and the AD2 is taped to the bottom of the motor mount. The servo mount is keyed to the WTC cylinder end and the motor mount is keyed to the servo mount. This ensures the AD2 is fixed in relation to the WTC mount. Finishing out the stern compartment is what I think of as the power distribution board. The ESC and both servos plug into this board which sends power from the ESC to the servos and also up to the Rx. Signal wires attach to the board before they run to the front compartment.


I put together a schematic of all the connections to make sure I didn't forget any and also to eliminate any redundancies.



Early in the WTC development I got tired of putting the parts into and out of the cylinder, so I printed a 1/2 cylinder to help with the assembly and fit testing. I was very pleased with how well it worked.



The ballast tank started with ordering a child sized blood pressure cuff. Then I got out my kitchen vacuum sealer and started cutting it down until it fit.



I milled the WTC slots for the ballast section on my CNC mill. I doubt I needed 30 holes, but the only example of an RCABS I had was Steve's Seawolf which had a ton of holes.



The front WTC was fairly simple to put together. Because of the low current draw I expected (<2 Amps) I set it up to connect only to the battery balance port and not the main connector. This allows charging and turning on the system without removing the battery from the WTC. In the bottom of the picture you can see the charging adapter which connects to the polarized Deans 4 pin connector that goes through the end bulkhead. To turn the system on there is a different to 4 pin connector that only connects the battery positive to the positive wire to the ESC.



All bulkheads were prototyped on the filament printer. Final bulkheads were printed on the resin printer to ensure close tolerances and also to be sure they were watertight.



The end of the WTC keys into a pin mounted in the hull. The pin locates the WTC and prevents it from rotating. A clamp at the front prevents the WTC from moving forward. In this picture you can also see the connectors for the servo linkages. I had planned to use magnetic connectors, but there just wasn't room. The short metal connectors are only about 1/2" long.

[RCENGR]

You can easily encase all the linkages within that stern:

Ironically, Steve sent me those very pictures as we were discussing linkages. Let's just say I know my limitations.

[Albacore 569]

Some detailed photos taken in San Diego, California. October 2006. Drydocking/ Decommissioning
prior to becoming a museum.

[RCENGR]

Thanks for the pictures, those should help Steve when he gets around to weathering the sub.

So I arrived at Subfest with the wiring of the sub incomplete. I worked Wednesday night, most of Thursday and into Friday to finish up the wiring and get the sub assembled. Friday afternoon we started testing the ballast. We added 2-3 ounces to the bottom of the hull and put it in water, where it promptly sank to the bottom. So we removed some lead and had the same result. At that point I knew that some foam needed to be added and we quit for the day.

At the AirBnB I added foam from the waterline down about 3/4". Then it was into the kitchen sink to test ballast again. It was still not positively buoyant. At that point I knew some major changes were needed. In order to play with the sub I pumped up the ballast bladder and ballasted it in that condition.

So on Saturday we did get the sub in the water. There was a snafu with the radio, so I pulled the 75 mHz Rx out and replaced it with a 2.4 GHz set from my surface ship. The sub ran at PD pretty well. After a while Steve let some air out of the ballast tank and started diving it dynamically. He was able to get it under the water about a foot before the loss of signal stopped everything and it slowly floated to the surface. So we did have fun with it, even if its performance was less than ideal.

Here's the current list of fixes:
- get the 75 mHz radio in
- work on the rudder linkage. It was a little stiff and had too much slop in it, resulting in a poor return to center. The hole in clevis I used was oversized, so I need to correct that to tighten up the linkage.
- there was a lot of torque roll under power. As I don't think I can ever get enough lead in the bottom to make it self righting, I plan to put some differential in the horizontal planes.
- there was some water in the motor compartment, so I need to track that down. I think the drive shaft cup seal is the likely culprit, which is just press fit in right now. I'll add some silicon to seal it.
- and lastly, more buoyancy is needed. For starters I'm going to shorten the ballast tank by 1". That should increase the buoyancy by about 20 grams. Next I'm going to replace the blood pressure cuff bladder with a balloon, which will fill the ballast tank better.

[RCENGR]

Here's a short video of the Dolphin in the water.

https://youtu.be/CfK__xXBNdw?feature=shared

[Albacore 569]

Historically, AGSS-555 is significant, perhaps as much as the more famous Albacore AGSS -569. as test platforms. But aesthetically it's about as sexy as a propane storage tank behind the ACE hardware.... lol. The two clip on towed array connections are interesting. Operationally, I would weather but maybe cut the weathering by half as seen on the photos as a modeler, but that's your discretion.

Dolphin launched a torpedo from the deepest depth that one has ever been fired. Other examples of Dolphin's work include:

• first successful submarine-to-aircraft optical communications
• development of a laser imaging system of photographic clarity
• development of an extreme low frequency antenna for Ohio class SSBN/SSGN's.
• Evaluation of various Non acoustic ASW techniques
• Evaluation of various low probability of interception active sonars
• First submarine launch of a mobile submarine simulator system
• First successful submarine test of BQS-15 sonar system
• Development of highly accurate (10 cm) towed body position monitoring system
• Development of a new obstacle-avoidance sonar system
• Development of a highly accurate target management system
• Evaluation of a possible "fifth force" of nature"
• First successful submarine-to-aircraft two-way laser communication
• Deepest submarine (i.e. (non-submergible) dive; Exceeded more than 3,000 feet (910 m).

[He Who Shall Not Be Named]

Here's a short video of the Dolphin in the water.

https://youtu.be/CfK__xXBNdw?feature=shared

The little sub that could.

[Subculture]

A trick or two to counter torque roll without a drastic overhaul.

Reduce the propeller pitch, then increase RPM to compensate for any loss of thrust.

Pack as much foam as you can into the hull then compensate with lead in the keel to increase mass of the boat and improve the metacentric height.

[RCENGR]

The updates to the Dolphin are finally finished. I started by shortening the ballast tank to get more buoyancy.

The new tank is just long enough to cover the holes that are already drilled in the cylinder. Since I printed the bulkheads on the resin printer, I decided to use transparent resin. I think they turned out very nice.


When I installed it, I added some foam rings to fill the spaces in the ends where the balloon can't reach.



The tank changes helped buoyancy significantly. Now the sub floats without the ballast tank being inflated. Additionally, it needed about 3 oz of lead to get to submerged trim.

[RCENGR]

The next problem was the slop in the rudder linkage. Looking at the EZ connector on the servo arm that is used to get linear motion, I realized the hole was just too big. The hole was 0.079" when it needed to be 0.0625" for the 1/16" rod. So I soldered a 3/32" OD tube into the EZ connector. I also sleeved the clevis where it connected to the rudder yoke. Overall this tightened up the rudder linkage significantly. The seals still have enough friction that the rudder is not self centering, but that is a minor problem.

[RCENGR]

To address the leakage in the stern compartment of the WTC I glued in the drive shaft cup seal with silicone. I also polished the stainless steel push rods with 600 grit sandpaper to make sure they worked smoothly though the o-rings. Then I pressurized the WTC and didn't find any leaks.There was some condensation visible in the WTC after running the sub for two hours. Overall I think this is good enough. I might get some UV leak detector and see if I can find where the water is entering, for possible improvement of future builds if nothing else.

[RCENGR]

To fix the torque roll, I put some counter roll in using the pitch planes. Additionally, I put a V bend in the push rod on the starboard side so that I could make fine adjustment at the pond. Overall this helped significantly. There was still some list, but part of that is due to ballast weights that are not quite right. Overall I was happy with the performance.

I didn't take a good picture of the V bend in the push rod, but you can see the point of the bend peeking out just in front of the planes.